The present invention relates to an optical device, an optical test bench and an optical test method.
In order to test an optical or optoelectronic observation system, hereinafter referred to as a unit to be tested, it is known to use an optical test bench comprising an optical device designed to form a test light wave with variable resolving power, i.e., which may be convergent, divergent or collimated.
The known optical device comprises a light source providing a light wave, called source light wave, a screen receiving the source light wave and concealing part thereof in order to provide a light wave, called test light wave, and a convergent optical lens (or equivalent), designed to receive the test light wave and having a focus on the side of the light source and the screen.
In particular, the lens may be replaced by a concave mirror.
In this known optical device, the light source and the screen can move together relative to the lens so as to place the screen behind the focus, at the focus or even in front of the focus of the lens or the concave mirror, such that the optical device respectively provides a divergent, collimated or convergent light wave.
The test light wave is designed to be received by the unit to be tested, which thus sees the test chart formed by the screen as if that test chart were situated at a distance comprised between a value below five kilometers and infinity (distance greater than five kilometers), depending on the resolving power of the test light wave.
The unit to be tested is then designed to focus on the test chart and to provide an image of that test chart to a computer device. The latter can perform different tests on the image so as in particular to assess the quality of focusing done by the unit to be tested.
The preceding known optical device has the problem that it is difficult to resituate the test chart precisely at the focus of the lens or the concave mirror. This replacement requires many manipulations and verifications of the position of the test chart. Furthermore, the mechanical system making it possible to place the test chart relative to the lens or concave mirror is complex and expensive.
However, such a replacement is necessary. For example, in order to determine the mechanical reference axis of the unit to be tested, it is known to perform an auto-collimation using a mirror reflecting the collimated test wave. However, if the screen is not precisely at the focus of the lens or the concave mirror, the reflected wave can no longer be observed by a video or optical viewing system.